The present invention relates to a sealing element for sealing a projectile against the leakage of gases there past.
More particularly, the present invention is related to providing a seal for a ballistic projectile to prevent erosion and/or failure of the interior ballistics propulsion system during the barrel travel phase of projectile launch.
When a projectile is launched in a gun barrel, it acquires its initial velocity from the propulsive effect of the gun propellant gas pressure. The gas pressure is applied over the cross sectional area of the projectile which is defined by the effective projectile diameter taken at some contact circumference along the bore of the barrel which corresponds to the sealing surface of the projectile.
If the projectile is of a material which may be deformed slightly by action of the gun gases upon it, the radial deformation of the projectile body may be employed to form the seal between itself and the gun bore. In order to improve the seal, almost all conceivable types of soft deformable materials have been used to seal the finite gap between the projectile and the barrel. Such materials have included cloth, paper, elastomeric materials, and various metals such as lead, copper and aluminum. The geometric deformation of the seal may be elastic and/or plastic.
One common method of providing a seal includes the manufacture of a shell having a circumferential groove therein into which a circular band of relativley soft metal is inserted by elastic stretching, plastic swaging or by welding/brazing methods. A commonly used material is gilding metal which is swaged in place. Gilding metal is an alloy of 95 percent copper and 5 percent zinc.
A need exists for a seal which will permit improved performance under more restricted and sophisticated design requirements.